The rapidly oscillating Ap (roAp) stars are cool, magnetic, chemically peculiar A-type stars which exhibit broad-band light variations with periods in the range 6-16 min and Johnson B semi-amplitudes typically mag (Kurtz 1990, Matthews 1991). These oscillations are caused by global non-radial acoustic pulsations, or `p modes', of low degree () and high overtone (). The roAp stars are thus of considerable significance because they allow the use of asteroseismology as a tool in the study of the chemically peculiar stars of the upper main sequence.
In an ongoing programme to search for new rapidly oscillating Ap stars in the southern sky, HD 213637 came to our attention as a candidate roAp star. HD 213637 is classified by Houk & Smith-Moore (1988) as A(p EuSrCr). The Strömgren indices of HD 213637 were measured to be , , , and . Our attention was particularly drawn to the dereddened indices, and , both of which indicate very strong metallicity and line blocking in the v band. As these are characteristics that we associate with the roAp stars, we decided to search for rapid oscillations in HD 213637.
© European Southern Observatory (ESO) 1998
Online publication: May 15, 1998